JP5569655B2 - Rubber composition for tire, pneumatic tire - Google Patents

Description

  The present invention relates to a rubber composition for a tire and a pneumatic tire that have improved low rolling resistance, wet grip properties and wear resistance as compared with conventional levels.

  In recent years, pneumatic tires for passenger cars have started a labeling (display method) system by JATMA (Japan Automobile Tire Manufacturers Association), and are required to achieve both low rolling resistance and wet grip performance at a higher level. In particular, the required level for wet grip performance is extremely high, and a pneumatic tire satisfying the wet grip performance grade a based on the labeling system has not been developed yet. At the same time, it is required to improve the wear resistance in order to extend the tire life.

  Conventionally, in order to improve the balance between low rolling resistance and wet grip properties, it is known to add silica to a rubber composition constituting a tread portion of a pneumatic tire. However, silica has a silanol group on its surface and tends to agglomerate, and its dispersibility may be insufficient due to its poor affinity with diene rubber. In this case, the loss tangent (tan δ) of the rubber composition, etc. There was a problem that the effect of modifying the dynamic viscoelastic properties could not be obtained sufficiently. Further, silica has a problem that the reinforcing property is small and the abrasion resistance is insufficient compared with carbon black, and the abrasion resistance is further lowered when the dispersibility is poor.

  For this reason, Patent Document 1 proposes to improve the low heat buildup and wear resistance by using a rubber composition containing a polybutadiene rubber modified with polyorganosiloxane or the like and silica. Although this rubber composition has an effect of improving low heat buildup and wear resistance, the demand level expected by consumers to improve low rolling resistance, wear resistance and wet grip properties is higher. There was a need to further improve the balance.

Japanese Unexamined Patent Publication No. 2009-84413

  An object of the present invention is to provide a rubber composition for a tire and a pneumatic tire in which low rolling resistance, wet grip properties, and wear resistance are improved to a level higher than conventional levels.

The rubber composition for a tire of the present invention that achieves the above object is based on 100 parts by weight of a diene rubber containing 5 to 50% by weight of a terminal-modified butadiene rubber (modified BR) having a vinyl unit content of 10 to 60% by weight. 2 to 50 parts by weight of an aromatic modified terpene resin having a softening point of 100 to 130 ° C., and 60 to 130 parts by weight in total of two types of silica X and silica Y, and the silica X and silica Y and optionally The ratio of silica to the total amount of reinforcing filler containing carbon black to be blended is 85% by weight or more, the nitrogen adsorption specific surface area of the silica X is 140 m ² / g or more, and the nitrogen adsorption specific surface area of the silica Y is 100 m. ² / g are beyond 140m less than ² / g, and x parts by weight the amount of the silica X with respect to the diene rubber 100 parts by weight, the mixing amount of the silica Y and y parts by weight , Fulfills the relation x / 7 <y ≦ x, the functional group of the modified BR is a polyorganosiloxane group, a hydroxyl group-containing polyorganosiloxane structure, an alkoxysilyl group, a hydroxyl group, an aldehyde group, a carboxyl group, an amino group , An imino group, an epoxy group, an amide group, a thiol group, and an ether group .
Moreover, the pneumatic tire of the present invention uses the tire rubber composition.

  The rubber composition for tires of the present invention is a diene rubber containing 5 to 50% by weight of a terminal modified butadiene rubber (modified BR) having a vinyl unit content of 10 to 60% by weight and a functional group reactive with a silanol group. 2 to 50 parts by weight of an aromatic modified terpene resin having a softening point of 100 to 130 ° C., limiting the blending amount of the two types of silica X and Y having the specific particle properties described above, and the total amount of reinforcing filler Since the silica ratio is 85% by weight or more, the dispersibility of silica can be improved, and the low rolling resistance, wet grip property and wear resistance can be improved to the conventional level or more.

The nitrogen adsorption specific surface area of the silica X is preferably 140 m ² / g or more and less than 185 m ² / g.

  As the functional group of the modified BR, a polyorganosiloxane group is preferable, and it has excellent reactivity with the silanol group on the silica surface, and can improve the dispersibility of silica.

  The pneumatic tire using the rubber composition for tires of the present invention can improve the low rolling resistance, wet grip properties and wear resistance from the conventional level.

It is a figure which shows the mixing | blending and evaluation of each composition of the Example of this invention, and a comparative example. It is a figure which shows the mixing | blending and evaluation of each composition of the Example of this invention, and a comparative example. It is a figure which shows the mixing | blending and evaluation of each composition of the Example of this invention, and a comparative example. It is a figure which shows the common compounding component used for each composition of the Example of this invention, and a comparative example.

  In the rubber composition for tires of the present invention, the rubber component is a diene rubber. In 100% by weight of the diene rubber, 5 to 50% by weight is terminal-modified butadiene rubber (hereinafter referred to as “modified BR”). The diene rubber can contain 25 to 95% by weight of other diene rubbers excluding the modified BR. Other diene rubbers include, for example, natural rubber, isoprene rubber, unmodified butadiene rubber, styrene butadiene rubber, end-modified styrene butadiene rubber, butyl rubber, isobutylene / p-methylstyrene copolymer rubber bromide, An example is ethylene-propylene-diene rubber. Of these, natural rubber, styrene butadiene rubber, terminal-modified styrene butadiene rubber, and bromide of isobutylene / p-methylstyrene copolymer rubber are preferable. The terminal-modified styrene butadiene rubber is contained in, for example, 25 to 66% by weight in 100% by weight of the diene rubber.

  The content of the modified BR is 5 to 50% by weight, preferably 10 to 35% by weight, based on 100% by weight of the diene rubber. For example, it is 17 to 30% by weight in 100% by weight of diene rubber. When the content of the modified BR is less than 5% by weight, the dispersibility of silica is insufficient, and the low rolling resistance and wear resistance cannot be sufficiently improved. On the other hand, when the content of the modified BR exceeds 50% by weight, the wet grip property is deteriorated.

  In the rubber composition of the present invention, the modified BR has a vinyl unit content of 10 to 60% by weight, preferably 10 to 30% by weight. For example, 10 to 12% by weight. When the vinyl unit content of the modified BR is less than 10% by weight, the affinity with silica is insufficient, and the low rolling resistance, wet grip property and wear resistance cannot be sufficiently improved. On the other hand, when the vinyl unit content of the modified BR exceeds 60% by weight, the rolling resistance is deteriorated. The vinyl unit content of the modified BR is measured by infrared spectroscopic analysis (Hampton method). The increase or decrease of the vinyl unit content in the butadiene rubber can be appropriately adjusted by a usual method such as a catalyst.

  In the present invention, the modified BR is a butadiene rubber in which both or one of its molecular ends is modified with a functional group having reactivity with a silanol group on the silica surface. The functional group that reacts with the silanol group is preferably a polyorganosiloxane group, a hydroxyl group-containing polyorganosiloxane structure, an alkoxysilyl group, a hydroxyl group, an aldehyde group, a carboxyl group, an amino group, an imino group, an epoxy group, an amide group, Examples thereof include at least one selected from a thiol group and an ether group. Of these, a polyorganosiloxane group is more preferable.

The polyorganosiloxane group is preferably a polyorganosiloxane having a structure of the following formula (I).

Wherein, R ¹ to R ⁸ is an alkyl group or an aryl group having 6 to 12 carbon atoms having 1 to 6 carbon atoms, may differ even these the same. X ¹ and X ⁴ is a group having a functional group capable of reacting with a terminal butadiene polymer chains, or an alkyl group or an aryl group having 6 to 12 carbon atoms having 1 to 6 carbon atoms, X ¹ and X ⁴ are each They may be the same or different. X ² is a group having a functional group that reacts with the end of the butadiene polymer chain. X ³ is a group containing 2 to 20 alkylene glycol repeating units, and a part of X ³ may be a group derived from a group containing 2 to 20 alkylene glycol repeating units. m is an integer of 3 to 200, n is an integer of 0 to 200, and k is an integer of 0 to 200.

  The method for preparing the modified BR used in the rubber composition of the present invention is not particularly limited, and a normal production method can be applied. As a suitable method for producing modified BR, for example, 1,3-butadiene polymerization is performed using a saturated hydrocarbon compound as a solvent and an organic lithium compound as a polymerization initiator, and the active terminal of the resulting butadiene polymer is obtained. Examples thereof include a method obtained by a modification reaction with a compound having a functional group capable of reacting with a polyorganosiloxane compound, more preferably a polyorganosiloxane compound having a functional group capable of reacting with an active terminal.

  In the present invention, by blending an aromatic modified terpene resin, it is possible to improve the balance between low rolling resistance and wet grip properties, and in particular to further improve wet grip properties. The aromatic-modified terpene resin has a softening point of 100 ° C. or higher, preferably 100 to 130 ° C. For example, it may be 105 to 125 ° C. If the softening point of the aromatic modified terpene resin is less than 100 ° C., the effect of improving wet grip properties cannot be obtained. The softening point of the aromatic modified terpene resin is measured based on JIS (Japanese Industrial Standards) K6220-1.

  Examples of the aromatic-modified terpene resin compounded in the tire rubber composition of the present invention include terpenes such as α-pinene, β-pinene, dipentene, limonene, camphene, and styrene, α-methylstyrene, vinyltoluene, phenol, indene. An aromatic modified terpene resin obtained by copolymerizing with an aromatic vinyl compound such as can be exemplified. Of these, styrene is preferred as the aromatic vinyl compound. As the aromatic modified terpene resin, commercially available products such as YS resin TO-125, TO-115, TO-105, and TR-105 manufactured by Yasuhara Chemical Co., Ltd. can be used.

  The compounding amount of the aromatic modified terpene resin is 2 to 50 parts by weight, preferably 5 to 50 parts by weight with respect to 100 parts by weight of the diene rubber. For example, it is 7.5 to 10 parts by weight. When the blending amount of the aromatic modified terpene resin is less than 2 parts by weight, the balance between the low rolling resistance and the wet grip property cannot be sufficiently increased. Moreover, when the compounding quantity of aromatic modified terpene resin exceeds 50 weight part, abrasion resistance will fall.

The tire rubber composition of the present invention, the nitrogen adsorption specific surface area of 140 m ² / g or more in which silica X, and nitrogen adsorption specific surface area are two of silica Y is less than 140 m ² / g exceed 100 m ² / g Silica X and Y are blended. By blending silica X and Y, the heat build-up of the rubber composition is suppressed, the rolling resistance when made into a tire is reduced, and wet grip properties and wear resistance can be improved.

Silica X to be used in the present invention, the nitrogen adsorption specific surface area of 140 m ² / g or more, preferably 150~230m ² / g, more preferably 150 meters ² / g or more 185m less than ² / g. For example, it is 160 to 185 m ² / g. By blending silica X having a small particle diameter in this way, wet grip properties and wear resistance can be ensured at a high level. When the nitrogen adsorption specific surface area of silica X is less than 140 m ² / g, wet grip properties and wear resistance are insufficient.

The silica Y is, 140 m less than ² / g specific surface area by nitrogen adsorption of greater than 100 m ² / g, preferably from 130m ² / g or less exceed 100 m ² / g, more preferably 105～130M ² / g. For example, it is 110 to 125 m ² / g. By blending silica Y having a relatively large particle diameter, it is possible to reduce rolling resistance when the tire is made particularly small and tires are formed. When the nitrogen adsorption specific surface area of silica Y is 100 m ² / g or less, the wet grip property cannot be improved. If the nitrogen adsorption specific surface area of silica Y is 140 m ² / g or more, the rolling resistance cannot be sufficiently reduced. In addition, the nitrogen adsorption specific surface area of silica X and Y shall be calculated | required based on the BET method of ASTM (American Society of Testing and Materials) D3037-81.

  In the present invention, when the blending amount of silica X with respect to 100 parts by weight of diene rubber is x parts by weight and the blending amount of silica Y is y parts by weight, the total amount (x + y) of silica X and Y is 60 to 130 parts by weight. The amount is preferably 80 to 130 parts by weight. For example, it is 80 to 130 parts by weight. When the total amount (x + y) of X and Y of silica is less than 60 parts by weight, the balance between low rolling resistance and wet grip properties cannot be sufficiently increased. When the total amount (x + y) of X and Y of silica exceeds 130 parts by weight, the rubber viscosity increases and the processability deteriorates. In addition, sufficient wear resistance cannot be ensured, and rolling resistance performance is greatly deteriorated.

  Moreover, the compounding amount x of silica X and the compounding amount y of silica Y need to satisfy the relationship x / 7 <y ≦ x. For example, it is necessary to satisfy x / 6 ≦ y ≦ x. Improving the balance between low rolling resistance and wet grip when the blending amount y (parts by weight) of silica Y is 1/7 or less (x / 7 or less) of the blending amount x (parts by weight) of silica X I can't. On the other hand, when the blending amount y (parts by weight) of silica Y exceeds the blending amount x (parts by weight) of silica X, the wet grip properties deteriorate.

  The rubber composition of the present invention may contain a reinforcing filler other than silica. Examples of other reinforcing fillers include carbon black, clay, talc, calcium carbonate, mica, and aluminum hydroxide. Among these, by always blending carbon black, it is possible to enhance the rubber reinforcement and ensure the dry grip performance and wear resistance. The amount of the other reinforcing filler is 0 to 19.5 parts by weight, preferably 3 to 15 parts by weight, based on 100 parts by weight of the diene rubber. For example, 5 to 10 parts by weight.

  The ratio of silica in the total amount of 100% by weight of the reinforcing filler containing silica X, Y and carbon black is 85% by weight or more, preferably 87 to 100% by weight. For example, 87.5 to 100% by weight of the total amount of the reinforcing filler is 100% by weight. If the ratio of silica is less than 85% by weight, the balance between low rolling resistance and wet grip properties cannot be improved. Here, the compounding amount of the reinforcing filler other than silica is such that the silica ratio in the total amount of the reinforcing filler of 100% by weight is 85% by weight or more, and the silica compounding amount is 100 parts by weight of the diene rubber. It is determined from 60 to 130 parts by weight.

  Silicas X and Y used in the present invention may be silicas having the above-described characteristics, and can be appropriately selected from those produced. Moreover, you may manufacture so that it may have the characteristic mentioned above by the normal method. As the type of silica, for example, wet method silica, dry method silica, or surface-treated silica can be used.

  In the rubber composition of the present invention, it is preferable to blend a silane coupling agent together with silica X and Y, so that the dispersibility of silica can be improved and the reinforcement to styrene butadiene rubber can be further enhanced. The silane coupling agent is preferably added in an amount of 3 to 15% by weight, more preferably 5 to 12% by weight, based on the amount of silica. For example, it is good to mix | blend 6.4-12 weight%. When the silane coupling agent is less than 3% by weight of silica, the effect of improving the dispersibility of silica may not be sufficiently obtained. On the other hand, when the silane coupling agent exceeds 15% by weight, the silane coupling agents are condensed with each other, and a desired effect may not be obtained.

  Although it does not restrict | limit especially as a silane coupling agent, A sulfur containing silane coupling agent is preferable, for example, bis- (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide. , 3-trimethoxysilylpropylbenzothiazole tetrasulfide, γ-mercaptopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, and derivatives thereof. Examples of the derivative include NXT-Z (manufactured by Momentive Performance).

  In addition to the fillers described above, tire rubber compositions are generally used for tire rubber compositions such as vulcanization or crosslinking agents, vulcanization accelerators, anti-aging agents, plasticizers, and processing aids. Various additives can be blended, and such additives can be kneaded by a general method to obtain a rubber composition, which can be used for vulcanization or crosslinking. As long as the amount of these additives is not contrary to the object of the present invention, a conventional general amount can be used. Such a rubber composition can be produced by mixing each of the above components using a known rubber kneading machine, for example, a Banbury mixer, a kneader, a roll or the like.

  The rubber composition for tires of the present invention can be suitably used for pneumatic tires, particularly tire tread portions. Pneumatic tires using this rubber composition have excellent wear resistance, low rolling resistance, excellent fuel efficiency, and excellent wet grip performance, equivalent to the wet grip performance grade a based on the JATMA labeling system. Have the ability to

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

4 types of rubber compositions for tires (Examples 1 to 7 , 10 to 12, Reference Examples 1 and 2 and Comparative Examples 1 to 21) having the composition shown in FIGS. ) Was prepared by adding sulfur and a vulcanization accelerator and kneading with an open roll to a masterbatch obtained by kneading and releasing components excluding sulfur and a vulcanization accelerator for 5 minutes with a 1.8 L closed mixer. In FIGS. 1 to 3, since the modified S-SBR and the unmodified SBR contain 37.5 parts by weight of oil-extended oil, the oil-extended oil is excluded in parentheses together with the actual amount in the amount column. The amount of each SBR net was shown. The blending amount of the aroma oil was adjusted as appropriate so that the total oil amount and / or rubber hardness in the rubber composition could be compared. The ratio of silica to the total amount of silica and carbon black is shown in the column “Silica ratio”. In addition, the quantity of the compounding agent described in FIG. 4 was shown by the weight part with respect to 100 weight part (net rubber amount) of the diene rubber described in FIGS.

  About 33 types of obtained rubber compositions for tires, tan-delta (60 degreeC) and abrasion resistance were measured by the method shown below.

tan δ (60 ° C)
The obtained 33 types of rubber compositions for tires were press vulcanized at 160 ° C. for 25 minutes in a mold having a predetermined shape to prepare vulcanized rubber samples. Using the viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., tan δ (60 ° C.) of the obtained vulcanized rubber sample was subjected to conditions of an initial strain of 10%, an amplitude of ± 2%, a frequency of 20 Hz, and a temperature of 60 ° C. Measured with The obtained results are shown in the “rolling resistance” column of FIGS. 1 to 3 as an index with the reciprocal of the value of Comparative Example 1 being 100. The larger the rolling resistance index, the smaller the tan δ (60 ° C.), the lower the heat generation, the lower the rolling resistance when made into a tire, and the better the fuel efficiency.

Abrasion resistance Lambone wear of the obtained vulcanized rubber sample was measured according to JIS K6264-2 using a lambone wear tester manufactured by Iwamoto Seisakusho under the conditions of a temperature of 20 ° C., a load of 15 N, and a slip ratio of 50%. It was measured. The obtained results are shown in FIGS. 1 to 3 as an index with the reciprocal of the value of Comparative Example 1 being 100. Higher index means better wear resistance.

  Next, four pneumatic tires having a tire size of 205 / 55R16 were manufactured by using the 33 types of tire rubber compositions described above for the tread portion. The wet grip properties of the 33 types of pneumatic tires obtained were evaluated by the methods shown below.

Wet grip property The obtained pneumatic tire is assembled to a wheel with a rim size of 6.5 × J and mounted on a test vehicle of 2.0 liter class, and the EU regulation wet grip grading test method (TEST METHOD FOR TYRE WET GRIP GRADING ( C1 TYPES)). The obtained results are shown in the column “Wet performance” of FIGS. 1 to 3 as an index with the value of Comparative Example 1 being 100. The larger the wet performance index, the better the wet grip performance.

In addition, the kind of raw material used in FIGS. 1-3 is shown below.
Modified BR1: butadiene rubber whose terminal is modified with a polyorganosiloxane group. It was prepared by the following production method so that the vinyl unit content was 12% by weight.

[Production Method of Modified BR1]
After charging 4000 g of cyclohexane, 600 g of 1,3-butadiene, and 0.28 mmol of tetramethylethylenediamine in an autoclave reactor with an internal volume of 10 L that was purged with nitrogen, n-butyllithium was converted into cyclohexane and 1,3-butadiene. An amount necessary for neutralizing impurities contained in the polymerization was added, and 7.7 mmol was added as an amount of n-butyllithium used for the polymerization reaction, and the polymerization was started at 50 ° C. After 20 minutes from the start of polymerization, 400 g of 1,3-butadiene was continuously added over 30 minutes. The maximum temperature during the polymerization reaction was 80 ° C. After completion of the continuous addition, the polymerization reaction was continued for another 15 minutes, and after confirming that the polymerization conversion rate was in the range of 95% to 100%, the reaction was stopped by adding excess methanol, and then the end of the polymerization reaction was stopped. After adding 0.027 mmol of polyorganosiloxane A containing glycidyl ether group in the form of a 20% xylene solution and reacting for 30 minutes, it corresponds to 2 mol of n-butyllithium used as a polymerization terminator. An amount of methanol was added to obtain a polymerization solution containing polybutadiene rubber. Thereafter, drying was performed in a dryer to obtain modified BR1. The vinyl unit content of the modified BR1 was measured by infrared spectroscopic analysis (Hampton method) and found to be 12% by weight.

Polyorganosiloxane A; a polyorganosiloxane having the structure of the following formula (I), m = 80, n = 0, k = 120, X ¹ , X ⁴ , R ^{1 to} R ³ , R ^{5 to} R ⁸ Are each a methyl group (—CH ₃ ) and X ² is a hydrocarbon group represented by the following formula (II):

Modified BR2: A butadiene rubber whose terminal is modified with a polyorganosiloxane group. It was prepared by the following production method so that the vinyl unit content was 8% by weight.
[Method for producing modified BR2]
A polymerization solution containing polybutadiene rubber was obtained in the same manner as modified BR1 except that the amount of tetramethylethylenediamine was changed to 0.07 mmol. Thereafter, drying was performed in a dryer to obtain modified BR2. The vinyl unit content of the modified BR2 was measured by infrared spectroscopy (Hampton method) and found to be 8% by weight.

BR1: Unmodified butadiene rubber having a vinyl unit content of 1% by weight, Nipol BR1220 manufactured by Nippon Zeon Co., Ltd.
BR2: Unmodified butadiene rubber having a vinyl unit content of 12% by weight, UBEPOL VCR412 manufactured by Ube Industries, Ltd.
-Modified S-SBR: solution-polymerized styrene butadiene rubber having a hydroxyl group at the end, Toughden E581 manufactured by Asahi Kasei Chemicals, vinyl unit content is 43% by weight, and contains 37.5 parts by weight of oil with respect to 100 parts by weight of rubber component Oil-extended product / unmodified SBR: Toughden 1834 manufactured by Asahi Kasei Chemicals Co., Ltd. Oil-extended product containing 10% by weight of vinyl unit and 37.5 parts by weight of oil to 100 parts by weight of rubber component. NR: natural rubber, SIR-20
Silica X1: Rhodia Zeosil 1165MP, nitrogen adsorption specific surface area of 160 m ² / g
Silica X2: Rhodia Zeosil 195GR, nitrogen adsorption specific surface area of 180 m ² / g
Silica X3: Rhodia Zeosil 200MP, nitrogen adsorption specific surface area of 220 m ² / g
Silica Y1: Rhodia Zeosil 115GR, nitrogen adsorption specific surface area of 110 m ² / g
Silica Y2: Ultrasil 5000GR manufactured by Degussa, with a nitrogen adsorption specific surface area of 125 m ² / g
Silica Z: Ultrasil 360 manufactured by Degussa, nitrogen adsorption specific surface area is 50 m ² / g
Carbon black: Show black N234 manufactured by Cabot Japan
Silane coupling agent: Sulfur-containing silane coupling agent, Si69 manufactured by Evonik Degussa
Modified terpene resin 1: aromatic modified terpene resin, YS resin TO-125 manufactured by Yasuhara Chemical Co., softening point 125 ° C.
-Modified terpene resin 2: Aromatic modified terpene resin, YS resin TO-85 manufactured by Yasuhara Chemical, softening point 85 ° C
Aroma oil: Showa Shell Sekiyu Extract No. 4 S

The types of raw materials used in FIG. 4 are shown below.
・ Zinc oxide: 3 types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd. ・ Stearic acid: Industrial stearic acid N manufactured by Chiba Fatty Acid Company
Anti-aging agent: Seiko Chemical Co., Ltd. Ozonon 6C
・ Sulfur: Fine powder sulfur with Jinhua seal oil manufactured by Tsurumi Chemical Co., Ltd. ・ Vulcanization accelerator 1: Noxeller CZ-G manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ Vulcanization accelerator 2: PERKACIT DPG manufactured by Flexis

As is apparent from FIGS. 1 to 3, the rubber compositions for tires of Examples 1 to 7, 10 to 12 and Reference Examples 1 and 2 have low rolling resistance (tan δ at 60 ° C.), wear resistance and wet grip. It has been confirmed that the performance is maintained and improved beyond the conventional level.

  In the rubber composition of Comparative Example 2, since the vinyl unit content of the modified BR2 is less than 10% by weight, wet grip performance and low rolling resistance performance are deteriorated as compared with Example 3. Since the rubber composition of Comparative Example 3 has a vinyl unit content of BR1 of less than 10% by weight and is not terminal-modified, wet grip performance and wear resistance are deteriorated as compared with Example 3. The rubber composition of Comparative Example 4 has a vinyl unit content of BR2 of 10% by weight or more but is not terminal-modified, so that the wet grip performance and the low rolling resistance performance are deteriorated as compared with Example 3. Since the rubber composition of Comparative Example 5 does not contain a modified terpene resin, wet performance and wear resistance are deteriorated as compared with Example 3. In the rubber composition of Comparative Example 18, since the amount of the modified terpene resin is less than 2 parts by weight, the wet performance is deteriorated. In the rubber composition of Comparative Example 19, since the blending amount of the modified terpene resin exceeds 50 parts by weight, the wear resistance is deteriorated.

  The rubber composition of Comparative Example 6 was blended with unmodified SBR having excellent wear resistance instead of the modified BR1, but the wear resistance was insufficient and the rolling resistance was deteriorated. In the rubber composition of Comparative Example 7, since the silica Y was not blended and the silica ratio in the total filler was less than 85% by weight, wet performance and rolling resistance were deteriorated. Since the rubber composition of Comparative Example 8 does not contain silica Y, the rolling resistance cannot be improved. In the rubber composition of Comparative Example 9, since the blending amount of silica Y is larger than the blending amount of silica X, the rolling resistance is improved, but the wet grip performance is deteriorated. In the rubber composition of Comparative Example 20, since the blending amount of silica Y was 1/7 or less of the blending amount of silica X, the wet grip performance and the low rolling resistance performance deteriorated. In the rubber composition of Comparative Example 21, since the total amount (x + y) of silica X and silica Y exceeds 130 parts by weight, sufficient wear resistance cannot be ensured, and the low rolling resistance performance deteriorates.

  In the rubber composition of Comparative Example 10, since the blending amount of the modified BR1 is less than 5% by weight, the low rolling resistance performance and the wear resistance performance are deteriorated. The rubber composition of Comparative Example 11 cannot improve the wet grip performance because the blending amount of the modified BR1 exceeds 50% by weight. In the rubber composition of Comparative Example 12, the total amount (x + y) of silica X and Y is less than 60 parts by weight, and the ratio of silica in the total filler is less than 85% by weight, so that the balance between low rolling resistance and wet grip properties is achieved. Can't be high enough. In the rubber composition of Comparative Example 13, since the total amount (x + y) of silica X and Y exceeds 130 parts by weight, the wear resistance cannot be sufficiently ensured, and the rolling resistance performance is greatly deteriorated. In the rubber composition of Comparative Example 14, the wet grip performance deteriorates because the softening point of the aromatic modified terpene resin 2 is less than 100 ° C.

Since the rubber composition of Comparative Example 15 was blended with two types of silica (silica Y2 and silica Z) having a nitrogen adsorption specific surface area of less than 140 m ² / g without using silica X, wet grip performance and abrasion resistance Sex worsens.

Since the rubber composition of Comparative Example 16 was blended with silica Z having a nitrogen adsorption specific surface area of 100 m ² / g or less instead of silica Y, wet grip performance and wear resistance deteriorate.

Since the rubber composition of Comparative Example 17 blended two types of silica (silica X1 and silica X3) having a nitrogen adsorption specific surface area of 140 m ² / g or more without using silica Y, the rolling resistance was deteriorated.

Claims (4)

For 100 parts by weight of a diene rubber containing 5 to 50% by weight of a terminal-modified butadiene rubber (modified BR) having a vinyl unit content of 10 to 60% by weight,
2 to 50 parts by weight of an aromatic modified terpene resin having a softening point of 100 to 130 ° C,
Two types of silica X and silica Y are blended in a total of 60 to 130 parts by weight,
The ratio of silica to the total amount of reinforcing filler containing silica X and silica Y and optional carbon black is 85% by weight or more,
The nitrogen adsorption specific surface area of the silica X is 140 m ² / g or more and less than 185 m ² / g,
The nitrogen adsorption specific surface area of the silica Y is less than 140 m ² / g exceed 100 m ² / g, and x parts by weight the amount of the silica X with respect to the diene rubber 100 parts by weight, y weight the amount of the silica Y And satisfying the relationship x / 7 <y ≦ x,
The functional group of the modified BR is polyorganosiloxane group, hydroxyl group-containing polyorganosiloxane structure, alkoxysilyl group, hydroxyl group, aldehyde group, carboxyl group, amino group, imino group, epoxy group, amide group, thiol group, ether A tire rubber composition, which is at least one selected from the group .   The tire rubber composition according to claim 1, wherein the functional group of the modified BR is a polyorganosiloxane group. The tire rubber composition according to claim 1 or 2 , wherein the diene rubber further contains 25 to 95 wt% of a terminal-modified styrene butadiene rubber. A pneumatic tire using a tire rubber composition according to any one of claims 1 to 3.